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Impagidinium aliferum
From Fensome et al., 2019:
Impagidinium aliferum Mudie, 1987, p.803, pl.4, figs.1a–b. Holotype: Mudie, 1987, pl.4, figs.1a–b. Age: Late Miocene–Late Pliocene.
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Original description: [Mudie, 1987]:
Impagidinium aliferum n. sp. (Plate 4, Figs, 1a, b)
Holotype. Plate 4, Fig. 1a, b; slide AGC 84103006, K28/1; Sample 607-23-6, 49-51 cm; GSC 55329, K 28/1.
Derivation of name. Latin ala (wing) and ferro (to bear).
Diagnosis. Cyst proximochorate with an asymmetrical ovoid main body that has an apical boss and widens in the antapical region. The paraplates are outlined by hyaline septa which are highest at the paraplate junctions, where they appear to be supported by thin rods. The
septa are lower between the paraplate junctions; however, the septa are high (> 10 µm) and finely reticulate between paraplates 1' ' and 2' ' and on the hypotract. An apparently tubular process is formed by septa surrounding the small posterior ventral paraplate. Paratabulation is
gonyaulacoid 4' , 6'' , 6c, 5''', 1p, 1'''', ?3s. Excystment is by loss of precingular paraplate 3'' .
Dimensions. Holotype: body length 60 µm, maximum width 50 µm, septa 13 to 20 µm wide. Range in body length 55 to 60 µm, maximum width 53 to 48 µm, maximum septum height 14 to 20 µm. Ten specimens measured.
Description. A large ovoid species of Impaginidium which has a very wide, finely reticulate septum on the epitract between paraplates
1'' and 2'' ; similar high septa border the posterior parasulcal area, giving the cyst an asymmetrical winged appearance. The parasulcus is very wide and extends far into the epitract, so that paraplates 1'' and 6'' are very narrow. A small apical boss is present, and there is a tubular process surrounding the posterior ventral platelet. Excystment is by loss of paraplate 3'' , which may initially remain attached to the epitract.
Remarks. This species is very similar in morphology to I. aculeatum (Wall) Harland, from which it differs in its much larger size, the presence of an apical boss, reticulate septa, posterior ventral tubular process, and much wider septa that give the cysts an asymmetrical winged appearance. The septal expansion in this species appears to represent a morphological transition between I. aculeatum, which has a few, relatively narrow septal expansions, and taxa such as I. japonicum and I. velorum, which are almost entirely covered by expanded septa.
Occurrence. Upper Miocene to upper Pliocene sediments at Site 611 and lower to upper Pliocene sediments at Site 607.
Impagidinium aliferum Mudie, 1987, p.803, pl.4, figs.1a–b. Holotype: Mudie, 1987, pl.4, figs.1a–b. Age: Late Miocene–Late Pliocene.
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Original description: [Mudie, 1987]:
Impagidinium aliferum n. sp. (Plate 4, Figs, 1a, b)
Holotype. Plate 4, Fig. 1a, b; slide AGC 84103006, K28/1; Sample 607-23-6, 49-51 cm; GSC 55329, K 28/1.
Derivation of name. Latin ala (wing) and ferro (to bear).
Diagnosis. Cyst proximochorate with an asymmetrical ovoid main body that has an apical boss and widens in the antapical region. The paraplates are outlined by hyaline septa which are highest at the paraplate junctions, where they appear to be supported by thin rods. The
septa are lower between the paraplate junctions; however, the septa are high (> 10 µm) and finely reticulate between paraplates 1' ' and 2' ' and on the hypotract. An apparently tubular process is formed by septa surrounding the small posterior ventral paraplate. Paratabulation is
gonyaulacoid 4' , 6'' , 6c, 5''', 1p, 1'''', ?3s. Excystment is by loss of precingular paraplate 3'' .
Dimensions. Holotype: body length 60 µm, maximum width 50 µm, septa 13 to 20 µm wide. Range in body length 55 to 60 µm, maximum width 53 to 48 µm, maximum septum height 14 to 20 µm. Ten specimens measured.
Description. A large ovoid species of Impaginidium which has a very wide, finely reticulate septum on the epitract between paraplates
1'' and 2'' ; similar high septa border the posterior parasulcal area, giving the cyst an asymmetrical winged appearance. The parasulcus is very wide and extends far into the epitract, so that paraplates 1'' and 6'' are very narrow. A small apical boss is present, and there is a tubular process surrounding the posterior ventral platelet. Excystment is by loss of paraplate 3'' , which may initially remain attached to the epitract.
Remarks. This species is very similar in morphology to I. aculeatum (Wall) Harland, from which it differs in its much larger size, the presence of an apical boss, reticulate septa, posterior ventral tubular process, and much wider septa that give the cysts an asymmetrical winged appearance. The septal expansion in this species appears to represent a morphological transition between I. aculeatum, which has a few, relatively narrow septal expansions, and taxa such as I. japonicum and I. velorum, which are almost entirely covered by expanded septa.
Occurrence. Upper Miocene to upper Pliocene sediments at Site 611 and lower to upper Pliocene sediments at Site 607.